Chances are you've set OFP's vertical refresh rate setting to a value not supported by your monitor.
To check this out, start the OFP preferences program and select a low resolution, such as 640 x 480. Save the setting and start OFP. If you can now see OFP's main menu, click on OPTIONS and then on VIDEO SETTINGS, where you can adjust the vertical refresh rate setting.
Once that's done you should be able to raise OFP's display resolution to something higher than 640 x 480 and execute OFP normally.